I've had three distinct careers: biomedical scientist; FDA drug regulator; and scholar at the Hoover Institution, a think-tank at Stanford University. During the first of these, I worked on various aspects of gene expression and regulation in viruses and mammalian cells. I was the co-discoverer of a critical enzyme in the influenza (flu) virus. While at the FDA, I was the medical reviewer for the first genetically engineered drugs and thus instrumental in the rapid licensing of human insulin and human growth hormone. Thereafter, I was a special assistant to the FDA commissioner and the founding director of the FDA's Office of Biotechnology. Since coming to the Hoover Institution, I have become well known for both contributions to peer-reviewed scholarly journals and for articles and books that make science, medicine, and technology accessible to non-experts. I have written four books and about 2,000 articles. I appear regularly on various nationally syndicated radio programs. My most frequent topics include genetic engineering, pharmaceutical development, and the debunking of various manifestions of junk science.

BPA Exposure Is 'Too Low to Cause Harm,' According To Regulators. But You'd Never Know That From The Media Coverage.

Suppose a new authoritative analysis revised the estimate of your lifetime chances of being struck by a meteorite — from, say, one in a hundred billion to one in ten billion. Should that tenfold increase in the probability make you any more worried? No– because both values are somewhere between negligible and infinitesimal.

A similar and more pertinent question of that type was posed by an announcement earlier this month by the European Food Safety Authority of a new “tolerable daily intake” (TDI) of a common industrial chemical called bisphenol-A (BPA). (BPA has been used for the past half century to make shatterproof polycarbonate plastics and is an ingredient in the epoxy safety liners of food and beverage cans that protect consumers from food poisoning.)

At the same time that regulators reduced the TDI for BPA, they emphasized that human exposure comes nowhere near the new, stricter limit – a critical point missed by many journalists and commentators.

TDI is an assessment of a person’s maximum daily intake of a substance that can occur every day for a lifetime without appreciable risks. It is based on studies of relevant animal species and is intentionally set very conservatively. In 2010, EFSA assessed BPA and set a TDI of 50 micrograms per kilogram of body weight per day. In the recent announcement, EFSA updated that assessment, proposing a reduced TDI of 5 micrograms per kilogram of body weight per day.

Chemical structure of bisphenol A. (Photo credit: Wikipedia)

The updated, reduced TDI, which was proposed to reflect data from new studies that have become available since 2010, represents a very conservative approach.

Taken at face value, this TDI reduction may appear to be an indictment of BPA and to reflect a risk to human health; and, predictably, many activists groups have touted the proposed change as such. But EFSA’s most significant finding is buried deep in news reports, if it is present at all: Even measured against the proposed reduced TDI, “EFSA finds there is no health concern, as the highest estimates for combined oral and non-oral exposure to BPA are 3-5 times lower than the proposed TDI, depending on age group.”

Bolstering that conclusion is a similar assessment last year by the U.S. Food and Drug Administration, which concluded that “BPA is safe at the very low levels that occur in some foods”–an assessment “based on review by FDA scientists of hundreds of studies including the latest findings from new studies initiated by the agency.”

EFSA used new data and information gleaned from more than 450 scientific studies to propose the lower TDI, which is essentially a distinction without a difference: Even assuming the highest exposure estimates for any age group, from fetuses to the elderly, BPA intake is well below the very conservative, updated TDI.

Putting it another way, although BPA’s TDI has been lowered, the practical impact remains the same: Whether 50 or 5 micrograms per kilogram, the TDI is set at a level to which humans are not likely to be exposed. Thus, reflecting a centuries-old tenet of toxicology that “the dose makes the poison,” BPA is not harmful to human health because the dose is far too low.

One key takeaway from this revelation is the need to take media reports on chemical regulation with a large grain of sodium chloride. The media like “if it bleeds, it leads” stories, especially if they involve certain activist-designated bogeymen, such as chemicals, nuclear power and genetic engineering. Often, the focus is on attention-grabbing headlines about shoddy studies or made-up phenomena, such as “BPA Exposure Linked to Prostate Cancer” or “Fukushima Radioactive Material Washed Up on California Beaches.” In this instance, however, we have an accurate, science-based report that received uncritical, flawed media coverage. One headline, for example, read, “EFSA Confirms the Hazards of BPA for Health.”

EFSA’s tenfold lowering of the TDI is analogous to a small increase in the odds of being struck by a meteorite: There’s no cause for heightened concern. The real story is that yet another careful analysis by a prominent regulatory agency has found that BPA poses negligible risk to human health.

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